This article presents novel defect review tool developed from CD-SEM, and its application for identification,
classification and judgment of false or nuisance defects.
Mask inspection tool is indispensable for mask production. Since conventional inspection tools use the optical source,
some of the defects are difficult to be identified and classified in the proper manner because the tool resolution is not
sufficient.
We have developed the Defect Imaging System (DIS-05) based on CD-SEM which uses secondary electron and
backscattered electron images. These SEM images are used for reviewing the defects detected in advance by optical
inspection tools. This system also includes Die-to-Die, Die-to-Database and "any shaped pattern area measurement" of
Holon original development.
The optical inspection system has been applied for mask inspection. The small but fatal detects on the mask can not be detected minutely by the optical system because of the limitations of optical resolution. We have developed the Defect Imaging System (DIS-05) using Backscattered Electron Images (BSI). DIS-05 is composed of 3 units: (1) SEM with a newly developed Backscattered Electron detector, (2) CAD computer to create CAD Image and, (3) Main computer to control the SEM and CAD computer. One of key technologies for DIS-05 is the technique of detecting BSI at a high contrast. Moreover, we herewith describe "Superimposed Image", which compares BSI with CAD one. Finally, we also report the possibility of detecting "haze on masks" using DIS-05.
Recently, in Critical Dimension (CD) measurement on high-end masks, Optical Proximity Correction (OPC) pattern measurement is on increase and it has become important to measure angled lines. In CD searching on a CAD layout viewer, the exact CD values can be detected for the OPC patterns because they consist of a lot of rectangles. While, the CD values for angled lines have not been detected in it. Meanwhile the mask Critical Dimension Scanning Electron Microscope (CD-SEM) can measure angled lines, but measurement accuracy cannot be verified because there is no reference standard sample available for calibration of the CD values. In this study, we made the prototype of a standard sample for CD measurement with 0 degree and 45 degree angled lines by using VLSI Standards Inc. Nano Lattice Standard. The shape is the same as 6025 mask. We measured CDs of angled lines of the above sample using Holon EMU-260 and examined the calibration
method. We are going to discuss the CD marking method on a CAD layout viewer in order to automate measurement of angled lines in near future.
Rapid changes in the feature size of photo masks have made it clear that there is an obvious limitation to the use of optical measurement tools, and mask makers now have the necessity to use CD-SEMs as a measurement tool for forefront patterns. The level of measurement precision and accuracy required for mask CD metrology has reached a point at which magnification calibration using the standard scale becomes indispensable. Since CD-SEM measurements are heavily influenced by local pattern irregularities compared to optical measurements, however, proper statistical treatment of data is necessary to estimate accurate values. In this paper, the tool repeatability, sample dispersion, line edge roughness amount and tool's long-term precision will be determined by the treatment of numerous measurement data. The general calibration of the tool is done by line pitch measurement of JQA standard, in that case the disagreement between line width measured values and user's desired values could be appeared. In this case we propose the method to change threshold value of measurement, and in this paper the evaluation of this method will be shown.
High density optical recording disk using vacuum evaporation deposited organic dye film is newly developed. As we investigate the signal characteristics of the vacuum evaporated disk in comparison with the disk fabricated by conventional spin-coat method, it is found that the vacuum evaporated disk has some features: to keep uniformity of tracking signal easily, high modulation, and wide power margin. Furthermore, it is clarified that the recording mechanism of the evaporated disk includes the hole formation by sublimation of the dye material. We confirm that the performance of the vacuum evaporated disk is high potentiality for DVD-R.
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